European 0,117,400 describes a nonagonal indexable cutting plate that has on its lower and upper sides several main and auxiliary cutting edges of different lengths and that has the form of an equilateral triangle with symmetrically beveled-off corners, the main cutting edges lying in the region of the beveled-off corners and being shorter than the secondary cutting edges. In order to make a large number of usable cutting edges in a small cutting insert it has been suggested to make the ratio of the lengths of the main cutting edges to the lengths of the secondary cutting edges between 1:1.5 and 1:3 and to merge the main cutting edges via rounded corners with the auxiliary cutting edges, the radii of the rounded corners generally corresponding to the radii of a perimeter circle of the indexable cutting plate.